1. Field of the Invention
The present invention is directed to fail-safe air actuated actuator mechanisms of the type which will automatically restore or return the valving member of a valve to a home or closed position, upon the occurence of a condition or particular contingency such as a power failure, pressure drop, or other change of conditions which could produce an element of danger or loss if the valve were permitted to remain open.
2. Description of the Prior Art
It is believed that applicant's U.S. Pat. No. 3,752,041 discloses the most relevant prior art. The fail safe actuator of that patent includes a fluid-operated vane motor having control-valve means connected between a source of pressurized fluid and one side of the motor, with a by-pass conduit having a restrictive orifice therein connected between opposite sides of the motor whereby a portion of the pressurized actuating fluid or media is diverted to an accumulator or storage tank, the contents of which are adapted to be discharged or unloaded on the other side of the motor to rotate the vane in an opposite direction to close a valving member operatively associated therewith.